No, it's not. One scorpion is simply fatter than the other. †It has nothing to do with the sex of it.

_________________"Life is a gamble. You can get hurt, but people die in plane crashes, lose their arms and legs in car accidents; people die every day. Same with fighters: some die, some get hurt, some go on. You just donít let yourself believe it will happen to you."-Muhammad Ali

Yes, the precise way is by the pectine count. As for H.longimanus, sexual dimorphism is usually physically visible but for most of the other heterometrus species, counting the pectines is the only sure way.